Bug 791352 - Screenshot delay is broken for region shots in GNOME.

Delay should indeed happen before root and window screenshots, but must
happen in-between region selection and region screenshot.
One can notice that the logics is different for Windows screenshot in
X11. The reason is that X11 window screenshot has an additional window
selection step (and therefore delay must happen in between selection and
actual screenshot). Window screenshot in Wayland doesn't have this step
and simply screenshots whatever is the currently active Window.